A method, system, and device for generating a clean clipping signal .alpha. for a chromakey function or a video composition, including identifying background colors formed by a solid color background, shadows cast by still and moving subjects, a non-uniform reflection caused by spot lighting and non-flat backdrop or flaw wall, and translucent foreground objects, with a 3D volume in a 3D color space; determining parameters defining same by using a dirty alpha .alpha.; generating a clean clipping signal .alpha..sub.shd background colors, and a clean clipping signal .alpha..sub.tsl for translucency colors; identifying foreground colors formed by the still and moving subjects with a 3D volume in a 3D color space; classifying colors into transition colors; and generating an area map for mapping each pixel into background, shadow, translucent, foreground, and transition areas.